As is well known in the nuclear reactor art, the reactor core fuel assemblies need to be periodically replaced in view of the fact that the nuclear fuel within the fuel assemblies becomes depleted as a result of the normal operation of the reactor facility. In accordance with conventional techniques or modes of operation, spent fuel assemblies are removed from the reactor core and replaced with new or fresh fuel assemblies by means of a refueling machine. The refueling machine conventionally comprises a trolley movable within a horizontal plane along a suitable track system disposed above the reactor core at an elevational height of, for example, thirty-five feet, and a vertically disposed outer or stationary mast is fixedly mounted upon the refueling machine trolley so as to be movable therewith. A vertically movable inner mast or gripper tube is co-axially disposed interiorly of the outer stationary mast, and a gripper assembly is fixedly secured to the lower end of the refueling machine gripper tube or inner mast. Guide pins are, in turn, fixedly secured to the lower end of the gripper assembly and are adapted to mate with suitable, correspondingly located apertures provided within the upper surface of each fuel assembly. Suitable gripper mechanisms or fingers are provided within the refueling machine gripper assembly for latchably mating with corresponding or cooperating structure of the fuel assembly nozzles, the gripper assembly guide pins serving to accurately align the gripper assembly with respect to the fuel assembly such that the gripper fingers may in fact latchably engage the fuel assembly nozzle structures. The latchable gripper mechanisms or fingers of the gripper assembly are movable between their latched and unlatched positions by means of an actuator mechanism disposed upon the lower end of a vertically movable, actuator tube co-axially disposed within the refueling machine gripper tube or inner mast.
In order to achieve the aforenoted alignment of the gripper assembly relative to the particular fuel assembly to be replaced so as to in fact achieve the aforenoted latching of the gripper mechanisms or fingers with the fuel assembly nozzle structure, it is imperative that the operator have a clear and unobstructed view of the fuel assembly nozzle. This, however, has proven to be a considerably difficult task to achieve when operating conventional refueling machines in view of the fact that the operator observes the fuel assembly nozzle structure through a suitable viewing aperture or window defined within the refueling machine trolley deck. Consequently it is readily appreciated that not only is the operator located a considerable distance away from the fuel assembly nozzle structure, but in addition, the reactor core cavity is entirely immersed within water. Therefore, light refraction causes distortion and an apparent erroneous location of the fuel assembly nozzles.
Still further, in order to view the fuel assembly nozzles, the operator must attempt the viewing operation from a position other than that which would be co-axial with the fuel assembly nozzles. Consequently, such an angularly offset location of the operator's viewpoint increases the aforenoted distortion, and therefore compounds the difficulty in accurately viewing the fuel assembly nozzle structures and obtaining the desired alignment of the gripper mechanism fingers therewith. In an attempt to resolve this problem, it has been proposed to employ television cameras mounted upon the outer stationary mast of the refueling machine. This technique, however, has likewise proven to be unsatisfactory in view of the fact that the fuel assemblies are nevertheless being viewed from a vantage point which is inclined or angularly oriented relative to a vertical axial plane of the fuel assemblies.
Accordingly, it is an object of the present invention to provide a new and improved nuclear reactor refueling machine.
Another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will overcome all of the aforenoted disadvantages of the conventional nuclear reactor refueling machines and the refueling operations characteristic thereof.
Still another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will greatly facilitate the alignment of the gripper assembly with the particular fuel assembly to be removed from the reactor core and replaced with a fresh or new fuel assembly so as to enhance the ease and efficiency of the nuclear reactor facility refueling process.
Yet another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will provide the refueling machine operator or personnel with a clear and unobstructed view of the fuel assemblies of the reactor core so that the gripper assembly of the refueling machine, and its gripper mechanisms or fingers, can be rapidly, easily, and accurately aligned with or positioned relative to the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies.
Still yet another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will permit the refueling machine operator or personnel, who is positioned at a location within the reactor facility which is remote from the reactor core and its fuel assemblies, to view the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies from a vantage point which is effectively within the immediate vicinity of the reactor core and the associated fuel assemblies.
Yet still another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will permit the refueling machine operator or personnel, who is positioned at a location within the reactor facility which is remote from the reactor core and its fuel assemblies, to view the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies from a vantage point which is directly above the particular fuel assembly which is to be removed from the reactor core and replaced with a fresh, new, or different fuel assembly such that the refueling machine operator's view of the particular fuel assembly is not angularly offset or oriented relative to the particular fuel assembly, or distorted by means of the light refraction properties of the water disposed within the reactor core cavity.